Water Journal : Water Journal July 2012
refereed paper public health water JULY 2012 79 Source tracking of faecal pollution Bacterial indicator organisms such as thermotolerant coliforms have been traditionally used for the measurement and monitoring of faecal pollution in waters (Geary and Davies, 2003). The presence of these faecal organisms on their own, however, does not necessarily indicate human contamination, as domestic livestock and wildlife are also potential sources of these organisms (Shah et al., 2007a). The presence of human faecal contamination in waters represents a higher health risk and, thus, regulatory bodies are concerned with differentiating human and non-human sources of faecal pollution (Mudge et al., 1999). The use of Microbial Source Tracking (MST) methods has been employed to facilitate this endeavour, which is expected to lead towards better management practices and more effective monitoring of faecal pollution in Australian watersheds (Ahmed et al., 2010). MST methods explore "signatures" of faecal indicator bacteria or compounds closely associated with them in order to detect and distinguish their sources (e.g. humans, animals, birds etc.) (Shah et al., 2007b). These MST methods widely fall into two basic categories: biological and chemical. Applications of MST methods such as faecal sterol ratios have been employed to facilitate this endeavour (Shah et al., 2006). Faecal sterols Coprostanol has been widely used as a chemical indicator of human sewage (Shah et al., 2007c). Coprostanol was found to be the major faecal sterol, constituting about 60% of the total sterols in human faeces (Leeming et al., 1996). It is produced by biohydrogenation of cholesterol by anaerobic bacteria in the intestines of humans and higher mammals. However, due to differences in diets of herbivores such as cows and sheep, 24-ethylcoprostanol, a derivative sterol, was suggested to be more prevalent in their excreta than coprostanol, while in dogs and birds faeces, cholesterol was shown to be not reduced to coprostanol due to lack of specific anaerobic bacteria in their digestive tract (Leeming et al., 1996). Considering all factors, Leeming et al. (1998) proposed sterol ratios to exploit faecal sterol "fingerprints" for the estimation of primary pollution originated from human and/or herbivore sources. Study Area and Methods Catchment description The Newcastle catchment covers an area of approximately 210km2 from Shortland and Glendale in the west to Charlestown in the south, and including Stockton located north of the harbour. The area is situated approximately 150km north of Sydney. The Newcastle catchment is located predominantly within the Newcastle City Local Government Area (LGA), with a small portion located within the Lake Macquarie LGA. In 2000, a population of over 130,000 lived in the Newcastle City LGA, which covered the majority of the catchment. At the time, the average annual rainfall in the Newcastle area was 1142mm (CH2M HILL, 2000a). The peak rainfall months are April, May and June, with the lowest rainfall occurring through September, October and November. Newcastle Harbour is a tidal system with most of its tributaries channelled into stormwater drains. Based on hydrological boundaries, the Newcastle catchment can be divided into four sub-catchments of Throsby Creek, Ironbark Creek, Cottage Creek and Hunter Estuary (Figure 1). Table 1 shows the principal land uses and possible pollutant sources in the sub- catchments of the Newcastle catchment at the time of the study in 2000. Within the Newcastle catchment there were approximately 30 premises licensed to discharge to waterways. Sampling and analysis Based on previous baseline water quality monitoring results and modelling developed to simulate the way the wastewater transportation system Table 1. Principal land uses and possible pollutant sources within sub-catchments of the Newcastle catchment. Sub-catchments of Newcastle Area (ha) Land Uses Possible Pollutant Sources Throsby Creek 3000 Predominantly urbanised, partly bushland/open space Wastewater discharge Urban/industrial run-off Point source discharges Ironbark Creek 12,500 Predominantly forests/rural and swamp land, partly urbanised Wastewater discharge/bypass Urban/industrial run-off Point source discharges On-site wastewater systems Cottage Creek 800 Predominantly residential, commercial Wastewater discharge Urban run-off Hunter Estuary 4700 Industrial/commercial, partly residential Wastewater discharge Urban/industrial run-off Point source discharges Recreational boating/fishing activities Source: CH2M HILL (2000a) Figure 1. Sub-catchments of the Newcastle catchment, NSW.
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